Pigments have been used in a variety of fields because each of them has a bright color tone, and high in coloring power and light resistance. Examples of a practically important material among them, in general, include a fine particle form of pigments. The pigments are formed into fine-particles preventing them from aggregation so that bright their color tone and high coloring power can be obtained. In this regard, in many cases, when the fine pigment particles are reduced in size by a physical method such as salt milling, the dispersion of fine pigment particles results in a high viscosity liquid. Consequently, when the pigment dispersion liquid is prepared on an industrial scale, there arise the following problems: the pigment-dispersion liquid prepared can not be taken out of a dispersion machine, the dispersion liquid can not be transported through a pipeline, and further the dispersion liquid is sometimes solidified into a gel form during its storage.
Therefore, conventionally, to solve these problems and to obtain a pigment-dispersion liquid or colored photosensitive composition improved in fluidity and dispersibility, it has been attempted to modify the surface of an organic pigment (see, for example, JP-A-11-269401 (“JP-A” means unexamined published Japanese patent application) and JP-A-11-302553) and to use various dispersing agents (see, for example, JP-A-8-48890 and JP-A-2000-239554). Further, reprecipitation of forming particles is disclosed in which a sample dissolved in a good solvent is injected into a poor solvent in, for example, JP-A-2004-123853 and JP-A-2003-336001.
For example, when colored images are formed using a colored photosensitive composition including such pigments, a layer made of the colored photosensitive composition is generally required to be very thin and to show a high color density even when the layer is thin. Therefore, for example, it is necessary to disperse highly and uniformly fine organic pigments in an organic solvent. However, there has been provided no pigment dispersion or no pigment dispersion composition satisfying such requirements and having good dispersibility, fluidity or the like.